om the big bang should still exist, and should therefore be detectable. This was the case in 1960 when background radiation was detected corresponding to the temperature predicted by Gamow's team. This discovery further supported the big bang theory. The big bang theory tries to explain what happened at or soon after the beginning of the universe. Today scientists can model the universe back to 10-43 seconds after the big bang. In the time before those 10-43 seconds, the classical theory of gravity is no longer adequate. Scientists are now searching for a theory that merges quantum mechanics and gravity, but have not found one yet. Many scientists hope that something called the string theory will tie together gravity and quantum mechanics and help scientists explore further back in time. Because scientists cannot look back in time beyond that early period, the actual big bang is hidden from them. Right now there is no way to detect the origin of the universe. The big bang theory does not explain what existed before the big bang either. It may be that time itself began at the big bang, so that there is no need to discuss what existed "before" the big bang. According to the big bang theory, the universe expanded rapidly during the first microseconds. The theory says that a single force existed at the beginning of the universe, and once the big bang occurred and the universe began to expand and cool, this single force separated into separate forces that we know today as: gravity, electromagnetism, the strong nuclear force, and the weak nuclear force. A theory called the electroweak theory now provides a unified explanation of electromagnetism and the weak nuclear force theory. Physicists are now searching for a grand unification theory to also incorporate the strong nuclear force. String theory seeks to incorporate the force of gravity with the other three forces. One widely accepted version of big bang ...
